Geothermal energy pros and cons

One of the biggest advantages of geothermal energy is that geothermal power is a very predictable and reliable source of energy, especially in comparison to other renewable energy resources like wind energy and solar energy. While wind and solar are more intermittent sources that require energy storage in order to be used most effectively at a large scale, geothermal power plants have a generally consistent power output no matter the time of day or season. This has many positive implications, notably that geothermal power is an appropriate source for meeting baseload energy demand.

Another advantage of geothermal power plants over other large-scale wind power, solar energy, or hydroelectric installations is the relatively low footprint of a geothermal plant. This is because, unlike wind, solar, and hydropower, geothermal energy comes from within the earth, and we don’t need to build out collection setups over large swaths of land surface to harness it. For reference, National Geographic estimates that a geothermal power plant capable of producing 1 gigawatt-hour (GWh) of electricity would take up approximately 404 square miles of land surface, while a wind farm at the same energy output would need about 1,335 square miles, and a solar farm would need about 2,340 square miles. That’s 88 percent less space for a geothermal power plant compared to a solar farm, both sized at 1 GWh.

Geothermal energy isn’t just for large power plants; in fact, one of the most efficient ways to use heat from the earth is to harness it with a geothermal heat pump for a residential or commercial building. Unlike geothermal power plants, geothermal heat pumps take advantage of low-temperature geothermal reservoirs which are available just about everywhere.

The geothermal energy industry is relatively young, and expanding with new technologies, research and development, and an influx of new projects. These enhancements to the industry are making geothermal energy more accessible, efficient, and applicable to a wider variety of use cases.

For example, a recent advancement in the geothermal energy extracting process, Enhanced Geothermal Systems (EGS), has made it possible to access deeper hydrothermal reservoirs. Hydrothermal reservoirs are where geothermal energy naturally occurs under the earth’s surface, and the deeper the reservoir, the less heat and steam actually makes it to the surface. EGSs create more open flow channels for steam to rise by fracturing rock with high speed water. Ultimately, this makes extracting geothermal energy from deeper reservoirs more feasible. 

Geothermal heating and cooling systems have a very long lifespan in comparison to many other green energy solutions. The US Department of Energy estimates a 20 year lifespan for heat pumps, and up to 50 years for the underground infrastructure. 

Unfortunately, geothermal power plants can’t be built anywhere. Geothermal reservoirs above 100°C are usually necessary for most large geothermal plants, and these reservoirs are only found in specific locations, usually near tectonic plate boundaries or hot spots. This is why the vast majority of U.S. geothermal power plants are in California: the state lies close to an active fault zone that is part of the larget “ring of fire” around the Pacific Ocean. Other parts of the country have lower temperature geothermal resources readily available, however, power plants are often not feasible.

The cost of deploying geothermal power plants is heavily skewed towards early expenses, as there are no fuel purchasing costs once the plant is up and running. According to Lazard’s LCOE analysis, the upfront cost to build a geothermal energy plant is between $4,000 and $6,000 per kilowatt-hour (kWh). Utility-scale solar energy maxes out at $1,250/kWh, and wind maxes out at $1,550/kWh, making geothermal electricity significantly more expensive upfront than other common renewable options. Even compared to combined-cycle gas plants, geothermal energy is four to six times as expensive initially.

The high upfront development costs associated with geothermal power plants is largely a function of the difficulty and cost of drilling deep into the earth to access geothermal reservoirs.

Constructing a geothermal power plant involves drilling deep within the earth to release hot steam and/or water trapped in rock formations. This process has been known to cause instability underground, which can lead to earthquakes at the surface of the earth. Additionally, geothermal power plants can cause slow land subsidence over time as geothermal reservoirs are depleted.